The present invention relates to telemetry systems in general, and more particularly to telemetry systems for medical purposes.
Telemetry is generally defined as a (more or less automated) communications process by which measurements are made and/or other data collected at remote or inaccessible points, and transmitted to a receiving equipment for monitoring, display, and/or recording. Originally, the information was sent over wires, but modern telemetry systems more commonly use radio transmission. Basically, the communication process is the same in either case. Among the major applications are monitoring electric-power plants, gathering meteorological data, monitoring manned and unmanned space flights, and more and more medical applications such as pulsoximetry or electrocardiography.
Telemetry systems normally comprise a transmitter for transmitting electromagnetic signals, e.g. from a measurement, and a receiver for receiving the electromagnetic signals from the transmitter. In current medical telemetry systems, the transmitter is usually carried by the patient and the receiver is typically installed in an operator room. Large systems may have a multitude of transmitters and receivers.
Each transmitter normally operates with a corresponding receiver on a certain channel, preferably over a pre-defined carrier frequency. Those channels, e.g. RF channels, are usually fixed programmed by the manufacturer. RF channels are related to RF carrier frequencies (e.g., in narrowband FM systems) or to coding (spreading) sequences in spread spectrum systems (e.g., direct sequence or frequency hopping systems). It is to be understood that the term `channel` is used herein in a very general sense and shall mean any communication channel which can be implemented by various technologies as known in the art, and is neither limited e.g. to certain fixed frequencies, nor to a certain transmission medium, or the like.
The currently available telemetry systems exhibit certain drawbacks:
The matching of each transmitter/receiver pair has to be identified by the operator. This is generally carried out by labeling each, transmitter and receiver, with the same channel number. PA1 In order to provide maintenance and application service, the channels must be tracked during their production process, throughout the entire ordering and service process, and at their place of application, such as a hospital. This leads to increased administration effort. However, in case that the channel assignment gets lost for certain reasons, it will become very difficult or even impossible to reassign the channel and to carry out certain services. PA1 If either the transmitter or the receiver fails or becomes inoperable for other reasons, that specific channel cannot be used anymore, since it is unique for each pair of transmitter and receiver. The channel is occupied until the component becomes operative again. Since the transmitter's battery is the most likely part to fail, this leads to designs, where the battery must be exchangeable by the operator.
A solution as known in the art for at least resolving some of the drawbacks is to provide a plurality of channels for the communication between the receiver and the transmitter(s), which can be manually selected for a specific transmitter/receiver pair.